Berlin prepares large thermos for winter

[TheVat]

With the Russian gas squeeze coming this winter, Berlin turns to a giant thermos...

https://apnews.com/article/russia-ukraine-technology-germany-berlin-trending-news-176229c8932869f45e553e615a6e9953

...of coffee hot water.  It will store off-peak wind and solar electricity production as heated water for use in home heating.  

Sometimes you have an abundance of electricity in the grids that you cannot use anymore, and then you need to turn off the wind turbines,” said Wielgoss. “Where we are standing we can take in this electricity.”

The 50-million-euro ($52 million) facility will have a thermal capacity of 200 Megawatts — enough to meet much of Berlin’s hot water needs during the summer and about 10% of what it requires in the winter. The vast, insulated tank can keep water hot for up to 13 hours, helping bridge short periods when there’s little wind or sun.

It will also be able to use other sources of heat — such as that extracted from wastewater, said Wielgoss. While it will be Europe’s biggest heat storage facility when it’s completed at the end of this year, an even bigger one is already being planned in the Netherlands.

I found the thirteen hours figure a little surprising.  With that much thermal mass, and the volume/surface ratio, and what I assume is excellent insulation, I would think it could stay pretty hot for longer than that.  Anyway, "cool" idea.

[MigL]

I like my idea better ...

Use 'excess' electricity, when available, to pump water to an elevated reservoir, then run the water down through turbines to generate electricity when there is demand.
Although there are pumping/generating losses, the 'elevated' water can be stored indefinitely, and won't 'run out' after 13 hours.

[StringJunky]

40 minutes ago, MigL said:

I like my idea better ...

Use 'excess' electricity, when available, to pump water to an elevated reservoir, then run the water down through turbines to generate electricity when there is demand.
Although there are pumping/generating losses, the 'elevated' water can be stored indefinitely, and won't 'run out' after 13 hours.

I like that idea, gravity is totally reliable. 

[exchemist]

53 minutes ago, MigL said:

I like my idea better ...

Use 'excess' electricity, when available, to pump water to an elevated reservoir, then run the water down through turbines to generate electricity when there is demand.
Although there are pumping/generating losses, the 'elevated' water can be stored indefinitely, and won't 'run out' after 13 hours.

Er, this has been done for decades. But it is not always easy to find suitable reservoirs at higher elevation.  

Edited July 1, 2022 by exchemist

[mistermack]

The current gas prices are making all sorts of projects viable, that were previously not. Hot water storage is fine, but you need a distribution network to get it to customers. I'm surprised that Berlin has enough network capacity to make this economic. Unless that is also just at the drawing board stage.

The wording of the statement is a bit fuzzy. Fifty million Euros doesn't sound like a major investment. And 10% of Berlin's hot water needs in the winter sounds impressive, but what exactly ARE Berlin's hot water needs? They don't say. 

The other problem is what happens if gas prices drop back down? Will it cut the legs from under this scheme? It's sure to make a huge difference to the economics if they do drop back. 

The other thing I find odd is the "up to 13 hours" figure. That strikes me as very poor, for a vast insulated tank. Insulation works better, for bigger tanks, because the surface area increases much slower than the volume for tank size increases. With modern insulating materials, I'm amazed that the figure isn't days, or weeks, rather than hours. 

[TheVat]

2 hours ago, mistermack said:

The other thing I find odd is the "up to 13 hours" figure. That strikes me as very poor, for a vast insulated tank. Insulation works better, for bigger tanks, because the surface area increases much slower than the volume for tank size increases. With modern insulating materials, I'm amazed that the figure isn't days, or weeks, rather than hours. 

 

7 hours ago, TheVat said:

I found the thirteen hours figure a little surprising.  With that much thermal mass, and the volume/surface ratio, and what I assume is excellent insulation, I would think it could stay pretty hot for longer than that...

I'll try tomorrow to get more deets.

[Ken Fabian]

Apparently Berlin has one of the biggest district heating systems in the world already in place - a couple of thousand km of pipework, with 3/4 of Berlin homes heated that way. A lot of it is waste heat from other energy use (co-generation) rather than made for the purpose. 

I suspect the "13 hours" refers to what will be available with expected use, not the time it can hold heat if none of it were being used. Whether heat pumps running from electricity would do it better or not making use of that infrastructure gives a big starting advantage to this kind of thermal storage over building pumped hydro and heating individual homes by other means. It may take an energy crisis or two and time to get significantly more pumped hydro, with reluctance to make those kinds of investments until it is clear it is essential, ie catching up or just in time rather than surging ahead of near future needs.

[MigL]

5 hours ago, exchemist said:

Er, this has been done for decades. But it is not always easy to find suitable reservoirs at higher elevation.

What has been done is the 'creation' of hydraulic gravitational potential in the form of hydroelectric dams.
My proposal would be for a hydroelectric 'battery', which stores electricity by raising water to a higher gravitational potential, and then re-extracting the electricity when the water drops back down through a turbine.

It could be as simple as a rooftop tank, to store electricity generated during the day by solar panels, and to recoup at night when the panels are not active.

[Ken Fabian]

21 minutes ago, MigL said:

It could be as simple as a rooftop tank, to store electricity generated during the day by solar panels, and to recoup at night when the panels are not active.

I am not sure that pumped hydro could be viable at such small scales, with such small differences in elevation. (I did attempt working out how much energy stored in 1 metric ton of water at 10m elevation and 100% efficiency but got caught by the conversion from joules to kWh (divide by 3.6 x 10⁶  ?) and got about 10 Watt hours but I have serious doubts I did the calculation correctly. Anyone know?). A few thousand tons of water would need stronger construction than the usual rooftop. Wouldn't heated water in an insulated tank do energy storage better on mass required basis? I think pumped hydro will only be viable at large scales where natural geography favours it.

Much simpler and cheaper at household level to add batteries. Ours work very reliably. Not sufficient for full heating (in a poorly insulated home in a mild climate) but significantly supplementing wood fired heating; we'd need about 3X current battery to ditch the wood but not much more solar. With respect to our costs it is more expensive than not having grid connected solar and batteries, but not a lot more (with value of blackout backup difficult to assess but a bonus). With power prices surging higher that may even have shifted to less expensive.

[Sensei]

9 hours ago, MigL said:

Although there are pumping/generating losses, the 'elevated' water can be stored indefinitely, and won't 'run out' after 13 hours.

2 cents:

1) water evaporates

2) water freezes in winter

8 hours ago, exchemist said:

Er, this has been done for decades. But it is not always easy to find suitable reservoirs at higher elevation.  

...it was much easier to "not shut down perfectly fine nuclear power plants after the Fukushima accident"....

Edited July 2, 2022 by Sensei

[exchemist]

6 hours ago, MigL said:

What has been done is the 'creation' of hydraulic gravitational potential in the form of hydroelectric dams.
My proposal would be for a hydroelectric 'battery', which stores electricity by raising water to a higher gravitational potential, and then re-extracting the electricity when the water drops back down through a turbine.

It could be as simple as a rooftop tank, to store electricity generated during the day by solar panels, and to recoup at night when the panels are not active.

Oh, maybe I misunderstood. Pumped storage hydro is well established: https://en.wikipedia.org/wiki/Pumped-storage_hydroelectricity 

Do you mean doing this at the level of the individual household, then? Have you done the calculation on what weight of water you need for a battery of adequate size? I have a feeling it might be rather large. But if you can give an idea of how many kWh storage would be needed, we can do the maths. 

P.S. Lifting 1mt through 1m gives you 10kJ, so if we take a 10 m high building, that would be 100kJ. Storage of 1kWh would require 3600kJ to be stored, i.e. 36mt water. That would require quite a structure to support it.  

Edited July 2, 2022 by exchemist

[mistermack]

Hazarding a guess, I would say that the 13 hours is more likely to be how long this tank can keep the district heating supplied if nothing else was generating heat. 

If Berlin already has a well developed district heating network, then it must have a well developed source of heat to supply it, so this storage tank is probably going to be taking heat from the current sources as well. It's likely to be doing the job of a capacitor, evening out the supply levels, rather than acting as a new source of renewable heat as portrayed.

[MigL]

9 hours ago, exchemist said:

Do you mean doing this at the level of the individual household, then? Have you done the calculation on what weight of water you need for a battery of adequate size?

It only has to store excess electricity generated by solar panels or windmills during he day, and is meant to offload drain on he grid.
Not be the sole supply.
And yes, at the household level batteries would be more efficient.
( but have you ever seen a Lithium fire when the batteries swell, crack and get wet ? )

[swansont]

23 hours ago, TheVat said:

I found the thirteen hours figure a little surprising.  With that much thermal mass, and the volume/surface ratio, and what I assume is excellent insulation, I would think it could stay pretty hot for longer than that.  Anyway, "cool" idea.

I think we’re swimming upstream of a press release/pop-sci filter. It says the capacity is 200 MW but that’s a power, so it doesn’t really make sense.

The 13 hours may be how long it stays hot enough to be usable, and safe. I found out recently there’s US building code/regulations/recommendations on minimum water heater temperature, below which Legionnaires’ disease becomes a risk. Probably don’t want to pump Legionella bacteria all around the city.

[J.C.MacSwell]

On 7/2/2022 at 3:16 PM, swansont said:

I think we’re swimming upstream of a press release/pop-sci filter. It says the capacity is 200 MW but that’s a power, so it doesn’t really make sense.

The 13 hours may be how long it stays hot enough to be usable, and safe. I found out recently there’s US building code/regulations/recommendations on minimum water heater temperature, below which Legionnaires’ disease becomes a risk. Probably don’t want to pump Legionella bacteria all around the city.

Water has excellent heat capacitance, and it's cheap, so it's kind of a shame you can't use a preheat tank at low to usable temperatures for hot water.

What you can do is have water storage tanks kept in a closed system that can be used for winter heating and/or summer cooling with a heat pump, especially if saved for times where the temperature differential makes heat pumps inefficient. Of course, the water may be cheap but the system and storage may not be.

Not sure if it was here on this site, but I seem to recall discussing a small community version of this being potentially efficient and easier to insulate (cube square rule) where much of the insulation can then be the ground itself as long as there were no underground water flows near the reservoir to steal the heat. More or less an augmented geothermal system.

Edited July 5, 2022 by J.C.MacSwell

[geordief]

There is this 100 tonne  sand battery in Finland  that goes to 500°C

https://www.bbc.com/news/science-environment-61996520

 

"Climate change: 'Sand battery' could solve green energy's big problem"

 

Plus this link from that BBC article 

 

https://www.nrel.gov/news/program/2021/nrel-options-a-modular-cost-effective-build-anywhere-particle-thermal-energy-storage-technology.html

Edited July 5, 2022 by geordief

[Ken Fabian]

8 hours ago, J.C.MacSwell said:

Water has excellent heat capacitance, and it's cheap, so it's kind of a shame you can't use a preheat tank at low to usable temperatures for hot water.

What you can do is have water storage tanks kept in a closed system that can be used for winter heating and/or summer cooling with a heat pump, especially if saved for times where the temperature differential makes heat pumps inefficient. Of course, the water may be cheap but the system and storage may not be.

Not sure if it was here on this site, but I seem to recall discussing a small community version of this being potentially efficient and easier to insulate (cube square rule) where much of the insulation can then be the ground itself as long as there were no underground water flows near the reservoir to steal the heat. More or less an augmented geothermal system.

There are examples of district heating using seasonal thermal storage using aquifers, tanks and the ground itself, eg like Drake Landing Solar Community in Alberta Canada that has 144 boreholes 34 metres into rock used as a heat store, replenished seasonally by solar collectors on the garages of participating homes during Summer. Not quite all their heating but always over 90%. Not sure what it would take for them to get to 100%.

I do think there is a lot of potential for ground source heat pumps for colder climates. Interesting that large buildings with borehole or thermal wall geothermal heating and cooling often have to have a cooling bypass to shed heat rather than pump it all into the thermal mass, because overall they are a heat source; the seasonal differences between taking heat out (Winter) and adding heat in (Summer) being out of balance can make the ground mass too hot (losing system efficiency?) over a few years.

Clearly we can use deep ground as inter-seasonal thermal storage and the rate of heat conduction is low enough that the surrounding rock is effectively it's insulation when the scale is large enough. So far as I can tell the up front capital costs are the barrier - despite often being cost effective over the longer term.

[mistermack]

17 hours ago, geordief said:

There is this 100 tonne  sand battery in Finland  that goes to 500°C

Heat loss grows faster and faster with temp increase, not linearly. ( can't be bothered to check the details ) So the insulation that works ok for 100 degrees would be no good at all for 500 deg. So you would have to spend a lot more money insulating this battery. 

100 tons of sand isn't all that big, really. It would fit in a 4m cube room. But presumably, with the insulation, and pipework for heat extraction, it would be somewhat bigger. 

I seem to remember I started a thread some time ago, proposing some form of heat/cold storage for new houses, either under the drive, or inbuilt as a cellar. I was proposing using water, but lots of storage mediums could be used. 

I just looked but didn't see it but found this :  

 

[Ken Fabian]

@mistermack I am still inclined towards boreholes into bedrock as the most widely available inter-seasonal thermal storage for heating buildings. High temperature storage can do other things but probably can't do building heating as cost effectively. It looks even better when large scale, ie district heating rather than one building at a time

From what I could find out about the Drake Landing example - and in keeping with my prior understanding - such heat masses need to be "primed" before the heat losses to surrounding rock slow sufficiently to give effective insulation; the first few years a lot more heat went in than came out but once the ground mass had gained enough heat the net flow out got a lot closer to the flow in. They claim Coefficient of Performance of 30 after the system was fully operational, ie 30x more heat than (non-solar) energy requirements, with more recent addition of solar PV to run the electricals. No heat pumps in that example so the storage mass must be hot enough to deliver water at temperatures high enough. Bigger storage mass and lower temperatures would use heat pumps.